The present invention relates to an apparatus for collecting and for cooling hot wire rod at the output of a rolling mill.
The apparatus according to the invention is suitably located at the output of a finishing rolling mill which in turn is arranged downstream a continuous casting machine such as of the type comprising a rotating casting wheel.
Different systems for collecting hot wire rods at the output of a rolling mill are used at present, which are suitably designed to be used with a particular kind of processed material. In fact a distinction should be made between easily heat oxidable material and other materials in which the heat oxidation problem is not critical or in any case does not involve particular protection measures being taken. This second type of material comprises, among other, steel wires, while the first type of material mainly includes copper wires.
For processing continuous steel rods or bars a number of systems have been suggested for collecting and cooling such rods or bars at the output of the working rolling mill, which prevailingly comprises tubular guide sections through which the wire coming from the rolling mill is caused to pass and in which such wire can be cooled by means of water jets or the like, a coiler located downstream the guides and capable of arranging the wire in a coil arrangement, and possibly a continuous conveyor arranged to carry the coils continuously formed by the coiler to one or more subsequent processing and/or cooling stations and then to a collection station for the wire in the form of skeins or the like.
The coilers are substantially of a first and second types. Coilers of the first type also known as "Garret" coilers, substantially comprise a rotating basket into which the wire rod is caused to move in a tangential direction and forms coils due to movement of inertia. This type of coiler is not suitable for a continuous casting owing to its limitations as far as skein dimensions are concerned and above all because the same fail to collect wire rod coming from the rolling mill at a speed higher than 20 m/sec (rolling speeds higher than 40-50 m/sec can be reached at present).
The coiler of the second type also known as "Edenborn" coiler collects the wire rod by forming circular coils be means of a rotating terminal arranged above the collection zone. This system can be used with rolling mills having an output speed of the wire rod also higher than 20 m/sec.
The above systems do not include special measures for avoiding the oxidation of the wire rod and have been suggested for those materials, such as steel, in which the oxidation problems are not critical also because during the previous working or milling steps they are already oxidized. In fact, such coiler systems are generally more suitable for production of substantial amounts of rod but of limited quality and in order to refine the quality of the product additional processing equipment is required which not only increases the overall dimensions of the whole production plant, particularly as far as the length thereof is concerned, but also involves high costs. As a matter of fact for the different operations additional equipment and apparatuses are necessary which due to both the number and dimensions thereof lead to a plant having a volume in excess relative to its productivity.
For collecting hot wire rods of an easily oxidable material such as copper, the above systems which do not include any particular provision for protecting the material against oxidation at the output of the rolling mill, either are not suitable or they are too much complicated and cumbersome.
For these materials a collecting and cooling system has been suggested which on the one hand causes wire rod to undergo a milling operation outside the contact with the air possibly in an artificial reducing atmosphere, and on the other hand it requires the cooling of the wire rod before the same is discharged from the processing plant down to a temperature at which no substantial oxidation occurs, the cooling being always made preventing the contact with the air, possibly also in an artificial reducing atmosphere.
At the output of the rolling mill a long tubular guide is provided along which the hot wire rod is caused to pass and is cooled by means of water supplied to the tubular guide and then discharged through suitable openings or ducts, thereby preventing oxidation from occurring and decreasing the wire rod temperature below the oxidation temperature before the wire rod comes out of the tubular guide.
In practice, such system has a number of limitations and numerous inconveniences.
First of all, such system does not allow to carry out a processing fast enough and this owing to the provision of the tubular guide. If the speed has to be increased, a longer guide has to be provided in order to ensure the necessary cooling before the wire leaves the guide. A longer guide on the one hand substantially increases the length of the whole plant (it is not suitable to provide a curved guide with U-return in order to reduce the overall dimensions lengthwise) and on the other hand a serious problem arises for a proper forward movement of the wire rod. As a matter of fact due to the requirements of the rolling operation, the hot wire rod comes out in such temperature and stiffness conditions that the same can be easily bent upon meeting an obstacle and abruptly terminates the feeding or forward movement with the danger of damaging the plant in which the upstream rolling mill continuously supplies wire rod at a high speed.
Secondly such system does not allow wire rod with a small diameter such as a diameter of 3 mm, to be processed, for example as taught in U.S. Pat. No. 3,810,371 in the name of Mario Propero filed on Oct. 28, 1971. As disclosed in the above mentioned Patent it is possible to obtain directly from a rolling mill a wire rod with a diameter between 3 and6 mm with a glossy surface, i.e. with a perfectly pickled surface at the output of the rolling mill. If such a small diameter has to be obtained in a plant including a collecting and cooling system as described above, a major problem arises due to the bending effect mentioned above. Also in order to obtain a satisfactory output per hour, the wire must be produced at a high speed (higher than 40 m/sec), such speeds being unpracticable, as stated above, in a system with a tubular guide specified above.
The systems at present in use for producing wire rod cannot thus be employed or they can be used with unsatisfactory practical and economical results when a reasonably high output per hour and a wire rod of high quality are required and even more when a small diameter wire rod has to be produced in the conditions specified above.